Many industrial, aerospace, and defense applications require air to be transferred via tubes from one location in a turbine engine to another. The air must often be robustly sealed from other air or fluid sources/sinks to avoid contamination or performance loss. For example, in a turbine engine, compressor air is often bled from the main core flow and routed through air transfer tubes to buffer sump cavities or to provide critical turbine airfoil cooling or turbine disk cavity purging. Unfortunately, the routing of the air requires that the inlets and exits of the transfer tubes be capable of significant relative motion (due to thermal expansion, vibration, or mechanical loads for example), which adds complexity to the design since multiple O-ring seals, piston seals, gasket seals, and associated mating bosses are required.
In addition, the transfer tubes often employ complex multi-piece assemblies and sub-assemblies that must be welded/brazed and inspected to ensure that the assembly is capable of fully sealing the respective flows. Stresses often concentrate at the junction of the thin walled tubes and the welded/brazed thick bosses or bends, which can result in thermo-mechanical fatigue failure at the stress concentrations in the assembly at the weak weld/braze joints and interfaces. Furthermore, the operating environment may include very high pressure differentials (up to 600 psig) and a demanding high temperature (up to 1200° F.). The resulting assemblies require multiple parts and/or sub-assemblies that must be purchased or fabricated and assembled or sub-assembled prior to engine build. Improperly assembled or failed joints and interfaces may result in air leakage, which could reduce engine performance and lessen engine cooling ability.
Prior art methods for fabricating air transfer tube assemblies include utilizing drawn tubes that require subsequent forming or bending to shape, followed by braze or weld operations to secure inlet and exit bosses and sealing grooves. The welded assemblies then must undergo weld inspections and pressure testing to ensure they meet design specifications. Some attempts have been made to utilize bellows to provide compliance in the assembly, but these manufacturing processes are expensive due to the roll-forming or expansive-forming fabrication techniques and subsequent brazing/welding processes that must be employed to produce the assembly. A limitation of roll-forming or expansive-forming technologies is the geometry or shape of the metallic bellows. Using current technology, a bellows can only be circumferential if produced via roll-forming and either round or nearly round if produced via expansive forming.
Prior art methods of sealing are thus non-optimal, and an innovative, “compliant” coupling seal configuration is needed to reduce part count, cost, and complexities of these assemblies while simultaneously providing more robust sealing and life. Additive manufacturing methods are now capable of fabricating compliant coupling seals as a single part without subassemblies—an enablement that is not possible using the prior art. The compliant coupler seal can also reduce chargeable cooling flows by eliminating leakages in the assemblies of prior art configurations. Furthermore, other desirable features and characteristics of the disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.